1. Field of the Invention
The present invention relates to transporting wafer-carrying pods between various processing tools within a bay of a semiconductor wafer fab, and in particular to an ergonomic pivoting handle assembly capable of rotating while the wafer-carrying pod is manually carried.
2. Description of the Related Art
A standardized mechanical interface (SMIF) system proposed by the Hewlett-Packard Company is disclosed in U.S. Pat. Nos. 4,532,970 and 4,534,389. The purpose of a SMIF system is to reduce particle fluxes onto semiconductor wafers during storage and transport of the wafers through the semiconductor fabrication process. This purpose is accomplished, in part, by mechanically ensuring that during storage and transportation the gaseous media (such as air or nitrogen) surrounding the wafers is essentially stationary relative to the wafers and by ensuring that particles from the ambient environment do not enter the immediate wafer environment.
The SMIF system provides a clean environment for articles by using a small volume of particle-free gas which is controlled with respect to motion, gas flow direction and external contaminants. Further details of one proposed system are described in the paper entitled "SMIF: A TECHNOLOGY FOR WAFER CASSETTE TRANSFER IN VLSI MANUFACTURING," by Mihir Parikh and Ulrich Kaempf, Solid State Technology, July 1984, pp. 111-115.
Systems of the above type are concerned with particle sizes which range from below 0.02 .mu.m to above 200 .mu.m. Particles with these sizes can be very damaging in semiconductor processing because of the small geometries employed in fabricating semiconductor devices. Typical advanced semiconductor processes today employ geometries which are one half micron and under. Unwanted contamination particles which have geometries measuring greater than 0.1 .mu.m substantially interfere with 1 .mu.m geometry semiconductor devices. The trend, of course, is to have smaller and smaller semiconductor processing geometries which today in research and development labs approach 0.2 .mu.m and below. In the future, geometries will become smaller and smaller and hence smaller and smaller contamination particles become of interest.
A SMIF system has three main components: (1) sealed pods, having a minimal volume, used for storing and transporting cassettes which hold the semiconductor wafers; (2) enclosures placed over cassette ports and wafer processing areas of processing equipment so that the environments inside the pods and enclosures (after having clean air sources) become miniature clean spaces; and (3) a transfer mechanism to load/unload wafer cassettes from a sealed pod without contamination of the wafers in the wafer cassette from external environments.
Typically a pod is transferred between various tools and other equipment within a bay of a semiconductor wafer fab. A tool bay may include on the order of approximately 15 to 20 process and metrology tools, one or more stockers for storing large numbers of pods, and a number of local tool buffers for storing pods adjacent to high throughput or metrology tools. Although many semiconductor wafer fab processes provide for an automated transport system, many times it is necessary to manually carry the wafer-carrying pod to or from a processing tool or lift or lower the pod onto a stocker or local tool buffer.
FIG. 1 illustrates conventional structures on a pod allowing the pod to be carried within a bay of a semiconductor wafer fabrication clean room. Typically, pods may be lifted from a 36-inch high work surface to a 52-inch high work surface. The pod 10 comprises a cover 12 including ergo handles 14 extending from the sides of the pod. The hands of a user are placed underneath the ergo handles 14, and a combination of upward force against the ergo handles and palm lifts the pod. The design of the pod 10 tends to force the user to adapt his or her wrist posture to the geometry of the pod and the pod handle design. When lifting or setting down a pod, the user's wrists tend to rotate in order to keep the pod vertical. This wrist rotation exerts a torque on the user's wrists. Moreover, fixed handles have a tendency to force the wrist into non-neutral postures even when no manual pod rotation is involved in handling the device. Furthermore, this design may lead to mishandling of the pod by the operator because transporting the pod is dependent on the operator's dexterity to support the pod in a vertical position.
The conventional way of transporting a pod was found to put undue pressure and stresses on the small joints of the hands (i.e. on the soft tissue of the palm near the thumb, called the Thenar muscle group) and wrists, as well as the larger supporting joints and muscles of the elbow, shoulder, and neck. Users often experience discomfort and, over time, develop tissue and nerve damage resulting in pain, weakness, burning, tingling and numbing in these areas. In the worst case scenarios, users may form tendinitis and carpal tunnel syndrome in their extremities. Moreover, a user's discomfort and tissue damage is often exacerbated by variations in human anthropometry, especially for smaller individuals, which are often not entirely accommodated in the design of the pod being carried. Anthropometry is the study and technique of human body measurement for use in anthropological classification and comparison. Furthermore, the weight of the pod which is typically 11 to 15 pounds, adds to the discomfort of the user when the pod is being repetitively lowered, lifted and rotated during transport to and from processing tools.
With the demand for ever-increasing output and production of semiconductor wafers, a redesign of the conventional method for carrying a pod in a labor intensive industry is required. In order to accommodate these demands, there is a need for a pod which includes an ergonomic handle design. Ergonomics is an interdisciplinary study that examines the relationship between workers and their work environment, the goal being to maximize worker comfort and efficiency in the workplace. Taking this into consideration, the ergonomic design of semiconductor equipment can result in reduced risk of injury, increased worker productivity, and reduced downtime during maintenance. SEMI S8 which is the "Safety Guidelines for Ergonomics/Humans Factors Engineering of Semiconductor Manufacturing Equipment" establishes criteria for the design of semiconductor manufacturing equipment where risk of injury or illness is minimized, and work productivity and comfort are enhanced. Specifically, SEMI S8-95 states that semiconductor manufacturing equipment should be designed to accommodate the physical dimensions of more than 90 percent of the user population and is directed towards minimizing the risk of upper extremity carpal tunnel disorder risk. Moreover, SEMI S8-95 provides handle design guidelines for device manufacturers and specifies that wrist deviation should not exceed 10 degrees, in order to minimize stresses at the wrist joint.
In an effort to improve the conventional handle design, a pod 14 having a pistol grip handle 16, as shown in FIG. 2, was developed in order to eliminate wrist motion fatigue and discomfort. However, this design, although providing a more comfortable grip for the user, did not eliminate the hand and wrist problems caused from handling the pod. The pistol grip remained perfectly vertical and stationary relative to the pod causing the user to adapt his/her wrist posture to the geometry of the pod and pod handles so that the pod also remained substantially vertical. As explained above, a handle design allowing the upper extremities to remain in neutral positions while the pod is transported to and from the processing tools or stocker is desired for elimination of user discomfort and injuries.